The present invention relates to an original document reader, and more particularly to an automatic background correction or an automatic amplitude control circuit for use in an original document reader capable of simultaneously scanning a plurality of lines on an original document to read information thereon.
In original document readers for use in a facsimile system and the like, it is known to simultaneously scan a plurality of lines to read information thereon. In this case, a different automatic background correction circuit or automatic amplitude control circuit is provided for the video signal output representative of an information on each respective line. Therefore, the number of circuit elements contained in an entire system becomes large, resulting in large-scale circuit construction and an increase in the manufacturing cost.